Brewing process | Brewery Boon

Geuze is blended, Lambic is brewed

Geuze is blended, not brewed. Geuze is created by combining several Lambic beers. Those Lambic beers, however, are brewed. Still with me? We are happy to show you all about the art of making Geuze.

Lambic is brewed with malt and wheat, but they are about the only things it has in common with other beers. Unlike other brewers, Lambic brewers do not add yeast to their brew. Lambic is made with a process referred to as spontaneous fermentation. All that is needed is the ambient air of the Zenne valley to work its magic on cold winter nights. This activates naturally occurring wild yeasts and bacteria in the brew, which is in an open cooling vessel.

Lambic we brew in the winter months is given ample time to mature in large oak barrels: our foeders. This allows the beer to continue to evolve thanks to the rich microculture living in these old oak barrels. Geuze is made by blending Lambic beers from different years – and therefore different foeders. Oude Geuze Boon for example, is a blend of Lambics that matured for 1, 2 and 3 years. That blend then undergoes several months of bottle conditioning, a second fermentation inside the bottle.

Spontaneous fermentation with well-considered processes

Oude Geuze Boon may well be our flagship product, but we offer a wide range of characterful beers. They owe their unique taste to various specific actions in the process. For example, our VAT Monoblends are mainly made with old Lambic from the same barrel, while our Black Labels are based on Lambic beers with the highest level of fermentation. We make our Oude Kriek and Framboise by adding fresh fruit to ferment together with young Lambic. We then use the resulting 'cherry Lambic' to create various beers with the expression of real fresh fruit.

Foeders with character

The lambic beers that we use to make our geuze also owe their character to the foeders in which they mature. Today, our brewery has 161 foeders: each one is an oak barrel with a long history. They have been used to mature lambic for several decades – a third of them for even more than a century.

The microflora of wild yeasts live in the oak of the foeder: they are fed by the lambic with which the barrel is filled each time. By repeatedly filling such an oak barrel with lambic over many decades, it becomes a lambic barrel. The microflora in such a cask ensure the maturation of the beer. By using the foeder again and again, the microflora also evolve over the years - with ever finer lambic as a result. The oldest casks in the brewery thus guarantee the finest, most delicious beer.

Our unique process

Geuze is blended, Lambic is brewed

Spontaneous fermentation with well-considered processes

Foeders with character

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